Role of the hypothalamic PVN in the reflex reduction in mesenteric blood flow elicited by hyperthermia.
The hypothalamic paraventricular nucleus (PVN) is an important integrative center in the brain. In the present study, we investigated whether the PVN is a key region in the mesenteric vasoconstriction that normally accompanies an increase in core body temperature. Anesthetized rats were monitored for blood pressure, heart rate, mesenteric blood flow, and vascular conductance. In control rats, elevation of core body temperature to 41 degrees C had no significant effect on blood pressure, increased heart rate, and reduced mesenteric blood flow by 21%. In a separate group of rats, muscimol was microinjected bilaterally (1 nmol/side) into the PVN. Compared with the control group, there was no significant difference in the blood pressure and heart rate responses elicited by the increase in core body temperature. In contrast to control animals, however, mesenteric blood flow did not fall in the muscimol-treated rats in response to the elevation in core body temperature. In a separate group, in which muscimol was microinjected into regions outside the PVN, elevating core body temperature elicited the normal reduction in mesenteric blood flow. The results suggest that the PVN may play a key role in the reflex decrease in mesenteric blood flow elicited by hyperthermia.
Chen
Feng
F
School of Medical Sciences, RMIT University, PO Box 71, Bundoora 3083, Melbourne, VIC, Australia.
Dworak
Melissa
M
Wang
Yuliang
Y
Cham
Joo Lee
JL
Badoer
Emilio
E
D000818:Animals; D001794:Blood Pressure; D001831:Body Temperature; D004195:Disease Models, Animal; D015536:Down-Regulation; D005334:Fever / Q000503:physiopathology*; D018755:GABA Agonists / Q000008:administration & dosage; D058785:GABA-A Receptor Agonists; D006339:Heart Rate; D008297:Male; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000187:drug effects; D012039:Regional Blood Flow; D013152:Splanchnic Circulation / Q000187:drug effects; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects
D018755:GABA Agonists; D058785:GABA-A Receptor Agonists; D009118:Muscimol